JPH05141959A - Screw effective diameter section deflection measuring device - Google Patents

Abstract

PURPOSE:To measure the deflection of an effective diameter section with a simple structure by moving a detector base synchronously with the rotation of a screw. CONSTITUTION:When the position of a screw groove 2 brought into contact with a probe 6 as a screw 1 to be measured is rotated is changed in the screw axis direction, the first arm 3 is rotated in the first plane parallel with the rotary shaft of a rotary base 16 centering on the first fulcrum 4, and the probe 6 is brought into contact with an effective diameter section. The probe 6 is fitted at one end of the second arm 7 supported by the second fulcrum 8, and the shift of the other end 9 is measured. The shift quantity of the other end 9 of the second arm 7 detected by a detecting means 10 is a value corresponding to only the deflection of the effective diameter section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring deflection of an effective diameter of a screw, and more particularly to an apparatus for measuring a screw such as a ball screw which requires high precision processing.

[0002]

2. Description of the Related Art There are outer diameter, inner diameter, pitch length, etc. as characteristics representing the shape of a screw, but the effective diameter is important when actually using the screw. When a normal screw or ball screw is used, the part related to the outer diameter or the inner diameter does not contact the other party, and does not affect the actual movement or engagement of the screw. FIG. 4 is a cross-sectional view showing a state in which hard balls are set on the ball screw, but it is clear that the outer diameter and the inner diameter do not contact the hard balls.
That is, the effective diameter determines the position accuracy of the hard sphere.

The thread groove has a spiral shape, and a three-dimensional coordinate measuring machine has conventionally been required to measure its shape. However, a three-dimensional coordinate measuring machine is expensive, and it is difficult to measure various thread-shaped items simultaneously and continuously, which requires time and labor for measurement. There was also a problem in measurement accuracy.

Therefore, the present applicant automatically moves the contactor to be pressed against the thread groove in accordance with the rotation of the thread to continuously and efficiently measure the cylindricity, pitch, and lead of the effective diameter of the thread. A screw measuring device is proposed in JP-A-62-214313.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The device proposed in Japanese Patent No. 14313 is a dedicated machine for efficiently measuring a screw, and the cylindricity of the effective diameter of the screw,
It can measure pitch and leads over a wide range. However, there is a demand for a device that can measure the characteristic relating to the effective diameter to some extent with a simple mechanism by using an ordinary roundness measuring device or the like instead of such a dedicated machine.

Of the characteristics relating to the effective diameter of the screw, the pitch has a considerable correlation with the pitch of the outer diameter, so that it is necessary to measure the deflection of the effective diameter. The deflection of the effective diameter corresponds to the circularity when the trajectory of the effective diameter is viewed from the direction of the screw axis. In the case of a ball screw, the circumscribing surface is formed by a plurality of hard balls as shown in Fig. 4, so the deflection of the effective diameter at each location and the lead error directly affect the lead and rattling when assembled. However, there is a problem that when the effective diameter fluctuates, abnormal noise is generated along with the movement. Therefore, it is important to measure the deflection of the effective diameter first.

The present invention has been made in view of the above problems, and an object of the present invention is to realize a measuring device capable of measuring the deflection of the effective diameter, which is a particularly important characteristic, with a simple structure.

[0008]

In order to solve the above-mentioned problems, a screw effective diameter portion measuring device of the present invention has a rotating table which rotates while holding a screw to be measured so that the screw shaft matches the rotating shaft. A first arm rotatably supported in a first plane parallel to the rotation axis of the turntable about the first fulcrum, and a first fulcrum provided on the tip of the first arm about the second fulcrum on the first arm A second arm rotatably supported in a direction perpendicular to the plane, a spherical probe that is provided at one end of the second arm and is in contact with the effective diameter portion of the thread groove of the screw to be measured, A detection unit that detects the amount of movement of the other end, and a biasing unit that biases the second arm so as to contact the thread groove of the screw measured by the probe.

[0009]

When the position of the screw groove in contact with the probe changes in the screw axis direction as the screw to be measured rotates, the first arm rotates in the first plane to bring the probe into contact with the effective diameter portion.
As a result, the amount of movement of the other end of the second arm detected by the detecting means has a value corresponding to only the shake of the effective diameter portion.

[0010]

EXAMPLES Before describing the examples, a brief description will be given of the measurement of runout of the effective diameter portion of the screw. FIG. 1 is a diagram showing the principle of measuring the runout of the screw effective diameter portion. Figure 1 (a)
In order to measure the deflection of the effective diameter portion, as shown in (1), a sphere in contact with the effective diameter portion is applied and the amount of movement in the radial direction is measured. Therefore, this sphere 6 is attached to one end of the second arm 7 supported by the second fulcrum 8 and the movement of the other end 9 is measured. Normally, the measurement sensitivity is increased by increasing the ratio of the distance between the probe 9 and the fulcrum 8 in the distance between the end 9 and the fulcrum 8. The amount of movement of the end 9 is detected by the detector 10.

To measure the deflection of the effective diameter, the screw 1 is rotated, but as shown in FIG. 1 (b), the position of the thread groove 2 in contact with the probe 6 changes with the rotation. Second arm 7
1 can rotate only within the plane of FIG. 1A, and as it is, it will come into contact with one of the screw grooves 2 as it rotates and will be displaced from the screw groove. Therefore, in order to measure the deflection of the effective diameter, it is necessary to move the detector base 101 in synchronization with the rotation of the screw 1. If this synchronism is deviated or the movement of the detector base 101 has a component in the plane of FIG.

It is conceivable to use a normal parallel moving means to move the detector base 101, but it is necessary to perform the synchronization control with high accuracy, and at the start of measurement, the probe is accurately set to the effective diameter portion. It is necessary to bring them into contact with each other, and it takes a lot of time and effort for initial setting. Therefore, in the present invention,
The portion mounted on the detector base 101 of FIG. 1 is provided at the tip of the first arm rotatable in a plane parallel to the screw axis. The first arm is supported by the first fulcrum and is balanced so that it can move smoothly even if a small force is applied. Therefore, when the screw groove 2 moves along with the rotation of the screw 1, the first arm rotates so that the tracing stylus 6 contacts the screw groove 2.

When the detector base 101 is moved, the components in the plane of FIG.
Compared with the parallel movement of 01, the rotating mechanism makes it easier to remove such an error factor and can be realized by a simple mechanism. FIG. 2 is a view showing an embodiment of a screw effective diameter portion deflection measuring device of the present invention. In FIG. 2, 1 is a screw to be measured, which is shown here as a ball screw. Two
Is the thread groove. Reference numeral 3 denotes a first arm, which is supported by a first fulcrum 4, a detector 12 is attached to one end, and a weight 5 is attached to the other end so that they are in balance with each other. Has been adjusted to.
As a result, the first arm 3 can rotate within a first plane parallel to the axis of the screw 1 only by applying a slight force, and a component outside this first plane is not generated in the rotation, or even if it exists, it can be ignored. It is a degree.

The detector 12 is equipped with the following items. The tracing stylus 6 is a sphere having a size in contact with the effective diameter portion of the thread groove 2, and is attached to one end of the second arm 7. The second arm 7 is supported by a second fulcrum 8 and is biased by a spring 11 so that the tracing stylus 6 contacts the thread groove 2.
The other end 9 of the second arm 7 is inside the differential transformer 11, and the position change of the end 9 can be detected. The second arm 7 is made to rotate perpendicular to the first plane on which the first arm 3 rotates.

To measure the deflection of the effective diameter portion of the screw, the detector 12 of the probe 6 having a diameter in contact with the effective diameter portion of the screw 1 to be measured is selected and attached to the first arm 3. Then, select the weight 5 that is in balance with this and adjust so that it is in perfect balance. The screw 1 is placed and fixed on the mounting base 13, and the tilt adjusting base 14 and the XY table 15 are adjusted so that the rotation axis of the mounting base 13 and the screw axis of the screw 1 substantially coincide with each other. These are on the rotating part 16 and are driven by the motor 17 to the gear 18
Is rotated through. It is desirable that the screw axis and the rotation axis are completely coincident with each other, but if the error is within a certain degree, correction by calculation is automatically performed.

The height of the first arm 3 is adjusted according to the portion of the fixed screw 1 to be measured, and the contact point 6 of the first arm 3 is shown in FIG.
Apply to the thread groove 2 as shown in. Since the second arm 7 is biased by the spring 11 and the first arm 3 rotates, the contact point 6 contacts the position corresponding to the effective diameter portion of the thread groove 2. In this state, the motor 17 is rotated and the differential transformer 10
Read and record the output of.

As the screw 1 rotates, the vertical position of the thread groove 2 with which the probe 6 contacts changes, but the first arm 3
Rotates to move the tracing stylus 6 along the screw groove 2, so that the tracing stylus 6 is in contact with the effective diameter portion of the screw groove 2, and a value corresponding to the deflection of the effective diameter portion is detected. The distance between the first fulcrum 4 of the first arm 3 and the probe 6 needs to be sufficiently longer than the length measured by the screw 1. This is because the contact position of the tracing stylus 6 slightly changes in the axial direction of the first arm 3 as the first arm 3 rotates, and this slightly affects the deflection of the effective diameter. The occurrence of this error will be described with reference to FIG.

In FIG. 3, the distance from the first fulcrum 4 of the first arm 3 to the probe 6 is R. It is assumed that the first arm 3 has now rotated ± α in the vertical direction. Then, the moving distance of the probe 3 in the vertical direction is ± Rα, which is defined as the measurement range. Therefore, when measuring one pitch, 2Rα corresponds to one pitch of the screw 1. At this time, the change in the position of the probe 6 in the axial direction of the first arm 3 is R (1-cosα).
Assuming that the radius of the effective diameter of the screw 1 to be measured is r, the effect on the deflection of the effective diameter is expressed by the following equation as shown in FIG.

R (1-cos (sin ^-1 R (1-cosα) / r)) (1) For example, when R = 200 mm and r = 10 mm, the measurement range is ±.
If the height is 5 mm, the error due to this is about 0.2 μm. Therefore, when measuring a few pitches of the screw, this error is hardly a problem. If it is necessary to measure over a wider range, measure within a range where error does not matter and repeat this.

[0020]

According to the present invention, it is possible to realize an apparatus capable of easily measuring the deflection of the effective diameter of a screw.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle of measuring runout of a screw effective diameter portion.

FIG. 2 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 3 is a diagram showing changes in measurement points due to rotation of a first arm.

FIG. 4 is a diagram showing an influence of an effective diameter error in a ball screw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Screw 2 ... Thread groove 3 ... 1st arm 4 ... 1st fulcrum 6 ... Measuring element 7 ... 2nd arm 8 ... 2nd fulcrum 9 ... The other end 10 ... Detection means (differential coil) 11 ... Energizing Means (spring) 16 ... Rotary table

Claims (1)

[Claims] 1. A rotary table which rotates by holding a screw to be measured so that a screw axis thereof coincides with a rotary axis, and rotates about a first fulcrum in a first plane parallel to the rotary axis of the rotary table. A first arm that is movably supported, and a second arm that is provided at the tip of the first arm and that is rotatably supported in a direction perpendicular to the first plane about a second fulcrum on the first arm. A spherical probe provided at one end of the second arm and in contact with an effective diameter portion of a screw groove of a screw to be measured, a detection unit that detects a movement amount of the other end of the second arm, A screw effective diameter part deflection measuring device comprising a biasing means that biases the second arm so that the probe contacts the thread groove of the screw to be measured.